1. Technical Field
The technology disclosed herein relates to camera systems, and more particularly, relates to a digital camera provided with a shake correction device.
2. Background Information
When an imaging device is shaken during photography, an optical image formed by an optical system is displaced relative to an imaging element, and the obtained image is probably blurred. Therefore, in order to decrease an influence applied by the shake of the imaging device to the image, a shake correction device is used.
For example, the shake correction device includes a correction unit for driving a correction lens, an angular velocity sensor for detecting a shake amount of a housing, and a correction control unit for controlling an operation of the correction unit according to output of the angular velocity sensor. In the imaging device on which the shake correction device is mounted, the correction lens is driven by the correction unit based on the shake amount detected by the angular velocity sensor so that the displacement of the optical image relative to the imaging element is restrained.
However, when the shake amount is large, it is sometimes not possible to sufficiently cancel out the displacement of the optical image even when the correction lens is driven to the limit of a movement enabled range. Therefore, in an imaging device of Japanese Patent Laid-Open Publication No. JP2005-176050, an exposure time during photography is set short in order to restrain an increase of shake amount. Moreover, in this imaging device, centering is executed before a start of the exposure so that the correction lens is returned to an initial position. Further, in the imaging device in Japanese Patent Laid-Open Publication No. JP2005-176050, when a plurality of images photographed in a short exposure time are overlaid, a synthesized image in which the influence of the shake of the imaging device is restrained is generated.
Japanese Patent Laid-Open Publication No. JP2008-107665 provides one countermeasure in a case where the influence of the shake of the imaging device is not sufficiently decreased by the shake correction device. Japanese Patent Laid-Open Publication No. JP2008-107665 discusses a technology for canceling a search operation when the shake of the imaging device is detected partway through an operation for searching a subject to be focused.
On the other hand, Japanese Patent Application Laid-Open Publication No. JP2004-282535 discusses a technology for detecting an object to be noticed from an image obtained by imaging. In this technology, even when the object is moving, the position of the object can be relatively accurately predicted by decreasing the influence exerted by the shake of the imaging device on the image.
Moreover, Japanese Patent Laid-Open Publication No. JP2007-243579 discuses a technology for calculating an error in the shake correction by comparing the shake amount and a movement amount of the correction lens. In this technology, a position at which an image signal representing a photographed image is cut is adjusted according to the error in the shake correction.
However, even when the centering is executed, the position of the subject on the image is deviated according to the shake amount of the imaging device at a time point at which the centering is ended. Thus, in order to generate the synthesized image as in the Patent Document 1, it is necessary to efficiently detect the change of the position of the subject on the image.
Likewise, when the influence of the shake of the imaging device is not sufficiently decreased by the shake correction device, it is necessary to efficiently detect the change of the position of the subject on the image in order to, for example, maintain a focal state on the subject by an autofocus operation.
Moreover, in order to accurately detect a moving object from the image, it is necessary to perform detection in consideration of the influence of the shake amount not compensated by the shake correction device.
On the other hand, when the influence of the shake of the imaging device within the exposure time is not sufficiently decreased by the shake correction device, the shake of the imaging device influences the image.
In this way, there is a desire for an imaging device capable of securing the processing accuracy for the photographed image even when the influence of the shake of the imaging device is not sufficiently decreased by the shake correction device.